Implantable Cardioverter-Defibrillator: What It’s for and What to Expect

Medically Reviewed By Uzochukwu Ibe, MD, MPH

An implantable cardioverter-defibrillator (ICD) is an electrical device that shocks the heart if it senses a dangerous heart rhythm. It can restore a more regular rhythm and prevent cardiac arrest. An ICD is also known as an implantable defibrillator or a defibrillator implant. Dangerous arrhythmias include ventricular tachycardia and ventricular fibrillation. They are more serious than other types of arrhythmias, such as atrial fibrillation (AFib). They can prevent your heart from pumping a sufficient amount of blood to your brain and body. They can also result in cardiac arrest.

Your doctor may recommend an ICD if you have had an episode of ventricular arrhythmia or you have a heart condition that increases your chance of cardiac arrest.

Keep reading to learn about ICD surgery, including how it is done, potential complications, and what to expect before, during, and after the procedure.

What is an ICD?

illustration of a dual chamber implantable cardioverter-defibrillator (ICD)
An illustration of a dual chamber implantable cardioverter-defibrillator (ICD). By Brittany England.

An ICD is a battery-powered device that a heart specialist inserts just under the skin in the upper chest. There are two parts: the electrical leads and the pulse generator, which is about the size of a pocket watch.

An implantable defibrillator works within the chest while an external defibrillator works outside the chest.

You may be familiar with the external type, also known as an automated external defibrillator (AED). If the AED senses an irregular heartbeat, the AED delivers a shock to restore a more normal heart rhythm. An AED increases the chance of survival Trusted Source American Heart Association Highly respected national organization Go to source from a malfunctioning heart and cardiac arrest.

Unlike an AED, an ICD tracks and treats the rhythm continuously.

What are the different types of ICDs?

The conventional type of implant is a transvenous ICD. The doctor places the pulse generator just beneath your collarbone. The leads connect the pulse generator to the heart through a vein.

A similar but newer type is the subcutaneous ICD Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source . The doctor places both the leads and the generator under the skin to the left of the breastbone. The leads are not in the heart.

Why is an ICD necessary? 

Your doctor may recommend Trusted Source American Heart Association Highly respected national organization Go to source an ICD if you have a known life threatening arrhythmia or a condition that increases the chance of developing one. Ventricular arrhythmias are particularly serious and can lead to sudden cardiac arrest.

Ventricular tachycardia is when your ventricles are beating too fast. Ventricular fibrillation is when your ventricles beat so fast and unevenly that they quiver, or shake. As a result of this fibrillation, the heart pumps little or no blood. Sudden cardiac arrest is possible. Defibrillation needs to occur within minutes to restore the heart rhythm.

Reasons for an ICD include:

How does defibrillation treatment feel?

Depending on your circumstances, your doctor can program the implantable defibrillator with the following functions:

  • pacing: If your rhythm is faster than it should be (according to the program), the ICD delivers several low energy “pacing” pulses, which may return the rhythm back to normal. You may feel a fluttering in your chest or nothing at all.
  • cardioversion: If pacing does not work, the ICD delivers a mild shock to stop the tachycardia. This can feel like being thumped in the chest.
  • defibrillation: If your heart is in fibrillation, the ICD will deliver a stronger shock, like being kicked in the chest. It may be painful but lasts less than a second.
  • pacemaker: If your rhythm is too slow, the ICD’s pacemaker function sends low energy pulses. The pacemaker can speed up the heart if defibrillation makes it too slow.

How do doctors implant the defibrillator?

Defibrillator implant procedures take place in a hospital. It is a minor operation performed under local anesthesia. An electrophysiologist — a cardiologist who specializes in arrhythmias — performs it.

For a transvenous ICD, your surgeon makes a small incision under the collarbone and inserts a catheter into a blood vessel. They thread the leads of the defibrillator through the vessel to the chambers on the right side of the heart. They place the pulse generator under the skin and attach the leads.

For a subcutaneous ICD, the doctor makes an incision to the left of the breastbone to install the device and leads.

The doctor tests and programs the device then closes the skin.

What preparation is necessary? 

You will undergo some tests and procedures beforehand. Preoperative testing may include:

Tell your doctor about all medications, vitamins, and herbal supplements you take. Additionally, inform the care team of any allergies or past allergic reactions you have experienced.

How long will it take to recover from the ICD procedure?

You may go home the same day or you may need to stay overnight in the hospital.

Recovery time varies. Most people return to light to moderate activities within a few days but check with your doctor. You may have to avoid strenuous activities for about a month after surgery. You will not be able to drive until your doctor says it is safe.

You may have mild pain, swelling, and tenderness at the placement site for several days after the surgery. Over-the-counter pain relievers can help reduce it. Discuss safe pain medication options with your doctor.

Device monitoring

Your doctor will test your ICD regularly. ICDs can transmit some information to your care team automatically and wirelessly, without you being there in person. This is called remote monitoring. It can help detect device and health issues early on. The ICD can:

  • monitor the pulse generator and the leads
  • record heart rate
  • record heart rhythm and arrhythmias
  • record pulses and shocks

A 2015 study in the Journal of the American College of Cardiology showed that remote monitoring increases survival.

Talk with your doctor about remote monitoring for your device.

What is it like living with an ICD?

Most people with ICD live as they usually would. You may need to make the following adjustments:

  • Alert your healthcare professionals that you have an ICD.
  • Carry an ID card that identifies your ICD device.
  • Avoid exposure to certain electrical devices or devices that have a strong magnetic field. Your doctor will provide specific instructions on ones to avoid. If you need an MRI, contact your doctor. Some new ICDs are MRI-compatible.
  • Use your cell phone on the ear opposite your device and do not keep it in your breast pocket.
  • Avoid contact sports and activities that could loosen your defibrillator leads.

Keep in mind that you may need future surgery to replace the battery, leads, or the entire ICD. Batteries generally last 5–7 years.

What are the risks and potential complications?  

In general, surgical risks include: 

Additional complications of an ICD may include:

  • blood clots or air bubbles in the vein
  • mechanical problems
  • heart or lung puncture
  • artery or vein tear
  • unnecessary pulses or shocks

You can help reduce the chance of certain complications by following your activity, dietary, and lifestyle restrictions and recommendations and taking your medications as directed. Some medications reduce the risk of unnecessary pulses.

Contacting your doctor

Keep your follow-up appointments and contact your doctor right away for:

  • bleeding more than expected
  • fever
  • increase in pain
  • unexpected drainage, pus, discoloration, or swelling of your incision
  • cardioversion event

Get immediate medical care (call 911) for:

Other frequently asked questions

Below are some other questions that people have asked about ICDs.

How long can you live with a defibrillator implant?

Keep in mind that the purpose of an ICD is to prevent sudden cardiac arrest. It does not cure the underlying reason for it. Studies show that ICD remote monitoring increases survival. Talk with your doctor about your long-term outlook with an ICD based on your overall health.

What is the difference between a defibrillator and a pacemaker?

A pacemaker takes over the electrical signals of the heart to maintain a regular rhythm. It is good for slow, fast, and uncoordinated heart rhythms. A cardioverter-defibrillator is a pacemaker with thicker insulated wires. This feature enables it to deliver shocks to stop ventricular fibrillation or cardiac arrest.

Is a defibrillator implantation major surgery?

A defibrillator implant is minor surgery. The physician makes a small incision in the upper chest to insert the pulse generator. They insert a catheter into a blood vessel and guide the leads to the heart.


An implantable defibrillator is a small device inserted into the upper chest and heart to monitor it for dangerous arrhythmias. If it senses one, it will deliver a strong shock to get the rhythm back to normal. For people at risk of developing a life threatening arrhythmia, a defibrillator implant can increase the chance of survival.

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Medical Reviewer: Uzochukwu Ibe, MD, MPH
Last Review Date: 2022 Sep 28
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